scholarly journals Requirement for Phospholipase C-γ1 Enzymatic Activity in Growth Factor-Induced Mitogenesis

1998 ◽  
Vol 18 (1) ◽  
pp. 590-597 ◽  
Author(s):  
Zhixiang Wang ◽  
Stefan Glück ◽  
Lianfeng Zhang ◽  
Michael F. Moran
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Phospholipase C ◽  
Cell Cycle Progression ◽  
Mdck Cells ◽  
Cell Receptor ◽  
S Phase ◽  
Dominant Negative ◽  
Nih 3T3 ◽  
Phase Entry

ABSTRACT The cytoplasmic regions of the receptors for epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) bind and activate phospholipase C-γ1 (PLC-γ1) and other signaling proteins in response to ligand binding outside the cell. Receptor binding by PLC-γ1 is a function of its SH2 domains and is required for growth factor-induced cell cycle progression into the S phase. Microinjection into MDCK epithelial cells and NIH 3T3 fibroblasts of a polypeptide corresponding to the noncatalytic SH2-SH2-SH3 domains of PLC-γ1 (PLC-γ1 SH2-SH2-SH3) blocked growth factor-induced S-phase entry. Treatment of cells with diacylglycerol (DAG) or DAG and microinjected inositol-1,4,5-triphosphate (IP3), the products of activated PLC-γ1, did not stimulate cellular DNA synthesis by themselves but did suppress the inhibitory effects of the PLC-γ1 SH2-SH2-SH3 polypeptide but not the cell cycle block imposed by inhibition of the adapter protein Grb2 or p21 Ras. Two c-fos serum response element (SRE)-chloramphenicol acetyltransferase (CAT) reporter plasmids, a wild-type version, wtSRE-CAT, and a mutant, pm18, were used to investigate the function of PLC-γ1 in EGF- and PDGF-induced mitogenesis. wtSRE-CAT responds to both protein kinase C (PKC)-dependent and -independent signals, while the mutant, pm18, responds only to PKC-independent signals. Microinjection of the dominant-negative PLC-γ1 SH2-SH2-SH3 polypeptide greatly reduced the responses of wtSRE-CAT to EGF stimulation in MDCK cells and to PDGF stimulation in NIH 3T3 cells but had no effect on the responses of mutant pm18. These results indicate that in addition to Grb2-mediated activation of Ras, PLC-γ1-mediated DAG production is required for EGF- and PDGF-induced S-phase entry and gene expression, possibly through activation of PKC.

scholarly journals Cellular Ras and Cyclin D1 Are Required during Different Cell Cycle Periods in Cycling NIH 3T3 Cells

1999 ◽  
Vol 19 (7) ◽  
pp. 4623-4632 ◽  
Author(s):  
Masahiro Hitomi ◽  
Dennis W. Stacey
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cyclin D1 ◽  
Cell Cycle Progression ◽  
Time Lapse ◽  
S Phase ◽  
3T3 Cells ◽  
Cycle Progression ◽  
Nih 3T3 ◽  
Nih 3T3 Cells

ABSTRACT Novel techniques were used to determine when in the cell cycle of proliferating NIH 3T3 cells cellular Ras and cyclin D1 are required. For comparison, in quiescent cells, all four of the inhibitors of cell cycle progression tested (anti-Ras, anti-cyclin D1, serum removal, and cycloheximide) became ineffective at essentially the same point in G1 phase, approximately 4 h prior to the beginning of DNA synthesis. To extend these studies to cycling cells, a time-lapse approach was used to determine the approximate cell cycle position of individual cells in an asynchronous culture at the time of inhibitor treatment and then to determine the effects of the inhibitor upon recipient cells. With this approach, anti-Ras antibody efficiently inhibited entry into S phase only when introduced into cells prior to the preceding mitosis, several hours before the beginning of S phase. Anti-cyclin D1, on the other hand, was an efficient inhibitor when introduced up until just before the initiation of DNA synthesis. Cycloheximide treatment, like anti-cyclin D1 microinjection, was inhibitory throughout G1 phase (which lasts a total of 4 to 5 h in these cells). Finally, serum removal blocked entry into S phase only during the first hour following mitosis. Kinetic analysis and a novel dual-labeling technique were used to confirm the differences in cell cycle requirements for Ras, cyclin D1, and cycloheximide. These studies demonstrate a fundamental difference in mitogenic signal transduction between quiescent and cycling NIH 3T3 cells and reveal a sequence of signaling events required for cell cycle progression in proliferating NIH 3T3 cells.

scholarly journals HTLV-I p30 inhibits multiple S phase entry checkpoints, decreases cyclin E-CDK2 interactions and delays cell cycle progression

2010 ◽  
Vol 9 (1) ◽  
pp. 302 ◽  
Author(s):  
Hicham H Baydoun ◽  
Joanna Pancewicz ◽  
XueTao Bai ◽  
Christophe Nicot
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Cyclin E ◽  
S Phase ◽  
Cycle Progression ◽  
Phase Entry

scholarly journals Expression of dominant-negative mutant DP-1 blocks cell cycle progression in G1.

1996 ◽  
Vol 16 (7) ◽  
pp. 3698-3706 ◽  
Author(s):  
C L Wu ◽  
M Classon ◽  
N Dyson ◽  
E Harlow
Keyword(s):  
Cell Cycle ◽  
Dna Binding ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Dominant Negative ◽  
Functional Domains ◽  
Dominant Negative Mutant ◽  
G1 Arrest ◽  
Wild Type ◽  
Cycle Progression

Unregulated expression of the transcription factor E2F promotes the G1-to-S phase transition in cultured mammalian cells. However, there has been no direct evidence for an E2F requirement in this process. To demonstrate that E2F is obligatory for cell cycle progression, we attempted to inactivate E2F by overexpressing dominant-negative forms of one of its heterodimeric partners, DP-1. We dissected the functional domains of DP-1 and separated the region that facilitate heterodimer DNA binding from the E2F dimerization domain. Various DP-1 mutants were introduced into cells via transfection, and the cell cycle profile of the transfected cells was analyzed by flow cytometry. Expression of wild-type DP-1 or DP-1 mutants that bind to both DNA and E2F drove cells into S phase. In contrast, DP-1 mutants that retained E2F binding but lost DNA binding arrested cells in the G1 phase of the cell cycle. The DP-1 mutants that were unable to bind DNA resulted in transcriptionally inactive E2F complexes, suggesting that the G1 arrest is caused by formation of defective E2F heterodimers. Furthermore, the G1 arrest instigated by these DP-1 mutants could be rescued by coexpression of wild-type E2F or DP protein. These experiments define functional domains of DP and demonstrate a requirement for active E2F complexes in cell cycle progression.

Selective Inhibition of CDK4 and CDK6 Primes Chemoresistant MCL Cells for Killing by Proteasome Inhibitor Bortezomib by Activating Cell Cycle-Coupled Apoptosis

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3624-3624
Author(s):  
Maurizio Di Li berto ◽  
Xiangao Huang ◽  
Amy Chadburn ◽  
Peter Martin ◽  
Ruben Niesvizky ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Growth ◽  
Cell Cycle Progression ◽  
Selective Inhibition ◽  
S Phase ◽  
Rational Approach ◽  
Effective Control ◽  
Cycle Progression ◽  
Selective Targeting ◽  
Phase Entry

Abstract Mantle Cell Lymphoma (MCL) remains generally incurable, suggesting that more effective control of unrestrained tumor growth is essential. Loss of cell cycle control is a hallmark of cancer, in particular of MCL where cell cycle progression through G1 is accelerated due to elevation of cyclin-dependent kinase 4 (CDK4) and constitutive cyclin D1 expression. Thus, one rational approach to improve MCL therapy is to target CDK4/6 in combination with cytotoxic killing. Although success in targeting the cell cycle in cancer with broad-spectrum CDK inhibitors has been modest, PD 0332991, the only known CDK4/6-specific inhibitor with oral bioavailability, has been shown to selectively and potently inhibit CDK4/6 in MCL cells ex vivo. Additionally, in a proof-of-mechanism study in patients with recurrent MCL, we have found that PD 0332991 is well tolerated, and effective in inhibiting CDK4 and CDK6 and suppressing tumor growth in vivo. Of note, 50% of the patients (8/16) have achieved a stable disease for greater then 40 weeks (Leonard et al, abstract submitted to ASH 2008). These findings suggest that selective targeting of CDK4 and CDK6 with PD 0332991 is a promising therapy for MCL. To advance targeting of the cell cycle in cancer, we have developed two novel approaches to both inhibit tumor cell proliferation and activate cell cycle-coupled apoptosis in MCL. We show in primary MCL tumor cells and MCL cell lines by BrdU pulse labeling and DNA content analysis that selective inhibition of CDK4/6 with PD 0332991 leads to a complete G1 arrest, despite high level of c-Myc expression and extensive chromosomal abnormality. As PD 0332991 acts reversibly, removal of PD 0332991 immediately releases the G1 block and induces synchronous (>90%) G1-S cell cycle progression and S phase entry. This sensitizes chemoresistant MCL cells to killing by suboptimal doses of cytotoxic agents such as bortezomib, through activating cell cycle-coupled apoptosis during S phase entry. Synergistic killing of MCL cells by induction of cell cycle synchronization with PD 0332991 in combination with bortezomib is mediated by induction of mitochondrial membrane depolarization and activation of caspase-9. In a complementary study, we have demonstrated that selective targeting of CDK4 and CDK6 by PD 0332991 similarly primes chemoresistant primary myeloma cells for cytotoxic killing by activating cell cycle-coupled apoptosis, and induces synergistic tumor suppression in animal models. Selective targeting of CDK4 and CDK6 by PD 0332991 in combination with cytotoxic killing, therefore, represents a promising new strategy for cell cycle-based therapy for MCL and other hematopoietic malignancies.

scholarly journals Cortactin Modulates RhoA Activation and Expression of Cip/Kip Cyclin-Dependent Kinase Inhibitors To Promote Cell Cycle Progression in 11q13-Amplified Head and Neck Squamous Cell Carcinoma Cells

2010 ◽  
Vol 30 (21) ◽  
pp. 5057-5070 ◽  
Author(s):  
David R. Croucher ◽  
Danny Rickwood ◽  
Carole M. Tactacan ◽  
Elizabeth A. Musgrove ◽  
Roger J. Daly
Keyword(s):  
Cell Cycle ◽  
Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Cell Cycle Progression ◽  
Kinase Inhibitors ◽  
S Phase ◽  
Cyclin Dependent Kinase ◽  
Cycle Progression ◽  
Fadu Cells ◽  
Phase Entry

ABSTRACT The cortactin oncoprotein is frequently overexpressed in head and neck squamous cell carcinoma (HNSCC), often due to amplification of the encoding gene (CTTN). While cortactin overexpression enhances invasive potential, recent research indicates that it also promotes cell proliferation, but how cortactin regulates the cell cycle machinery is unclear. In this article we report that stable short hairpin RNA-mediated cortactin knockdown in the 11q13-amplified cell line FaDu led to increased expression of the Cip/Kip cyclin-dependent kinase inhibitors (CDKIs) p21WAF1/Cip1, p27Kip1, and p57Kip2 and inhibition of S-phase entry. These effects were associated with increased binding of p21WAF1/Cip1 and p27Kip1 to cyclin D1- and E1-containing complexes and decreased retinoblastoma protein phosphorylation. Cortactin regulated expression of p21WAF1/Cip1 and p27Kip1 at the transcriptional and posttranscriptional levels, respectively. The direct roles of p21WAF1/Cip1, p27Kip1, and p57Kip2 downstream of cortactin were confirmed by the transient knockdown of each CDKI by specific small interfering RNAs, which led to partial rescue of cell cycle progression. Interestingly, FaDu cells with reduced cortactin levels also exhibited a significant diminution in RhoA expression and activity, together with decreased expression of Skp2, a critical component of the SCF ubiquitin ligase that targets p27Kip1 and p57Kip2 for degradation. Transient knockdown of RhoA in FaDu cells decreased expression of Skp2, enhanced the level of Cip/Kip CDKIs, and attenuated S-phase entry. These findings identify a novel mechanism for regulation of proliferation in 11q13-amplified HNSCC cells, in which overexpressed cortactin acts via RhoA to decrease expression of Cip/Kip CDKIs, and highlight Skp2 as a downstream effector for RhoA in this process.

scholarly journals Multiple requirements for SHPTP2 in epidermal growth factor-mediated cell cycle progression.

1996 ◽  
Vol 16 (3) ◽  
pp. 1189-1202 ◽  
Author(s):  
A M Bennett ◽  
S F Hausdorff ◽  
A M O'Reilly ◽  
R M Freeman ◽  
B G Neel
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Map Kinase ◽  
S Phase ◽  
Immediate Early ◽  
Kinase Activation ◽  
Epidermal Growth ◽  
Tyrosyl Phosphorylation ◽  
Phase Entry

Using transient overexpression and microinjection approaches, we examined SHPTP2's function in growth factor signaling. Overexpression of catalytically inactive SHPTP2 (PTP2CS) but not catalytically inactive SHPTP1, inhibited mitogen-activated protein (MAP) kinase activation and Elk-1 transactivation following epidermal growth factor (EGF) stimulation of 293 cells. An SHPTP2 mutant with both C-terminal tyrosyl phosphorylation sites converted to phenylalanine (PTP2YF) was also without effect; moreover, PTP2YF rescued PTP2CS-induced inhibition of EGF-induced Elk-1 transactivation. PTP2CS did not inhibit transactivation by activated Ras, suggesting that SHPTP2 acts upstream of or parallel to Ras. Neither PTP2CS nor PTP2YF inhibited platelet-derived growth factor (PDGF)-induced Elk-1 transactivation. Thus, protein-tyrosine phosphatase activity, but not tyrosyl phosphorylation of SHPTP2, is required for the immediate-early responses to EGF but not to PDGF. To determine whether SHPTP2 is required later in the cell cycle, we assessed S-phase entry in NIH 3T3 cells microinjected with anti-SHPTP2 antibodies or with a glutathione S-transferase (GST) fusion protein encoding both SH2 domains (GST-SH2). Microinjection of anti-SHPTP2 antibodies prior to stimulation inhibited EGF- but no PDGF- or serum-induced S-phase entry. Anti-SHPTP2 antibodies or GST-SH2 fusion protein could inhibit EGF-induced S-phase entry for up to 8 h after EGF addition. Although MAP kinase activation was detected shortly after EGF stimulation, no MAP kinase activation was detected around the restriction point. Therefore, SHPTP2 is absolutely required for immediate-early and late events induced by some, but not all, growth factors, and the immediate-early and late signal transduction pathways regulated by SHPTP2 are distinguishable.

scholarly journals Blocking the transcription factor E2F/DP by dominant-negative mutants in a normal breast epithelial cell line efficiently inhibits apoptosis and induces tumor growth in SCID mice.

1996 ◽  
Vol 183 (3) ◽  
pp. 1205-1213 ◽  
Author(s):  
R C Bargou ◽  
C Wagener ◽  
K Bommert ◽  
W Arnold ◽  
P T Daniel ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Tumor Growth ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Dominant Negative ◽  
Serum Starvation ◽  
Cycle Progression ◽  
Transcription Factor E2f

The transcription factor E2F is regulated during the cell cycle through interactions with the product of the retinoblastoma susceptibility gene and related proteins. It is thought that E2F-mediated gene regulation at the G1/S boundary and during S phase may be one of the rate-limiting steps in cell proliferation. It was reported that in vivo overexpression of E2F-1 in fibroblasts induces S phase entry and leads to apoptosis. This observation suggests that E2F plays a role in both cell cycle regulation and apoptosis. To further understand the role of E2F in cell cycle progression, cell death, and tumor development, we have blocked endogenous E2F activity in HBL-100 cells, derived from nonmalignant human breast epithelium, using dominant-negative mutants under the control of a tetracycline-dependent expression system. We have shown here that induction of dominant-negative mutants led to strong downregulation of transiently transfected E2F-dependent chloramphenicol acetyl transferase reporter constructs and of endogenous c-myc, which has been described as a target gene of the transcription factor E2F/DP. In addition, we have shown that blocking of E2F could efficiently protect from apoptosis induced by serum starvation within a period of 10 d, whereas control cells started to die after 24 h. Surprisingly, blocking of E2F did not alter the rate of proliferation or of DNA synthesis of these cells; this finding indicates that cell-cycle progression could be driven in an E2F-independent manner. In addition, we have been able to show that blocking of endogenous E2F in HBL-100 cells led to rapid induction of tumor growth in severe combined immunodeficiency mice. No tumor growth could be observed in mice that received mock-transfected clones or tetracycline to block expression of the E2F mutant constructs in vivo. Thus, it appears that E2F has a potential tumor-suppressive function under certain circumstances. Furthermore, we provide evidence that dysregulation of apoptosis may be an important step in tumorigenesis.

scholarly journals β1 integrin and IL-3R coordinately regulate STAT5 activation and anchorage-dependent proliferation

2005 ◽  
Vol 168 (7) ◽  
pp. 1099-1108 ◽  
Author(s):  
Paola Defilippi ◽  
Arturo Rosso ◽  
Patrizia Dentelli ◽  
Cristina Calvi ◽  
Giovanni Garbarino ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Endothelial Cells ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Janus Kinase ◽  
Serine Phosphorylation ◽  
Β1 Integrin ◽  
Adherent Cells ◽  
Cycle Progression ◽  
Phase Entry

We previously demonstrated that integrin-dependent adhesion activates STAT5A, a well known target of IL-3–mediated signaling. Here, we show that in endothelial cells the active β1 integrin constitutively associates with the unphosphorylated IL-3 receptor (IL-3R) β common subunit. This association is not sufficient for activating downstream signals. Indeed, only upon fibronectin adhesion is Janus Kinase 2 (JAK2) recruited to the β1 integrin–IL-3R complex and triggers IL-3R β common phosphorylation, leading to the formation of docking sites for activated STAT5A. These events are IL-3 independent but require the integrity of the IL-3R β common. IL-3 treatment increases JAK2 activation and STAT5A and STAT5B tyrosine and serine phosphorylation and leads to cell cycle progression in adherent cells. Expression of an inactive STAT5A inhibits cell cycle progression upon IL-3 treatment, identifying integrin-dependent STAT5A activation as a priming event for IL-3–mediated S phase entry. Consistently, overexpression of a constitutive active STAT5A leads to anchorage-independent cell cycle progression. Therefore, these data provide strong evidence that integrin-dependent STAT5A activation controls IL-3–mediated proliferation.

scholarly journals A cell cycle and mutational analysis of anchorage-independent growth: cell adhesion and TGF-beta 1 control G1/S transit specifically

1993 ◽  
Vol 122 (2) ◽  
pp. 461-471 ◽  
Author(s):  
EK Han ◽  
TM Guadagno ◽  
SL Dalton ◽  
RK Assoian
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Cell Cycle Progression ◽  
Fibroblast Cell ◽  
Tgf Beta ◽  
Cycle Progression ◽  
Anchorage Independent Growth ◽  
Differential Effects ◽  
3T3 Fibroblasts ◽  
Nih 3T3

We have examined cell cycle control of anchorage-independent growth in nontransformed fibroblasts. In previous studies using G0-synchronized NRK and NIH-3T3 cells, we showed that anchorage-independent growth is regulated by an attachment-dependent transition at G1/S that resembles the START control point in the cell cycle of Saccharomyces cerevisiae. In the studies reported here, we have synchronized NRK and NIH-3T3 fibroblasts immediately after this attachment-dependent transition to determine if other portions of the fibroblast cell cycle are similarly regulated by adhesion. Our results show that S-, G2-, and M-phase progression proceed in the absence of attachment. Thus, we conclude that the adhesion requirement for proliferation of these cells can be explained in terms of the single START-like transition. In related studies, we show that TGF-beta 1 overrides the attachment-dependent transition in NRK and AKR-2B fibroblasts (lines in which TGF-beta 1 induces anchorage-independent growth), but not in NIH-3T3 or Balb/c 3T3 fibroblasts (lines in which TGF-beta 1 fails to induce anchorage-independent growth). These results show that (a) adhesion and TGF-beta 1 can have similar effects in stimulating cell cycle progression from G1 to S and (b) the differential effects of TGF-beta 1 on anchorage-independent growth of various fibroblast lines are directly reflected in the differential effects of the growth factor at G1/S. Finally, we have randomly mutagenized NRK fibroblasts to generate mutant lines that have lost their attachment/TGF-beta 1 requirement for G1/S transit while retaining their normal mitogen requirements for proliferation. These clones, which readily proliferate in mitogen-supplemented soft agar, appear non-transformed in monolayer: they are well spread, nonrefractile, and contact inhibited. The existence of this new fibroblast phenotype demonstrates (a) that the growth factor and adhesion/TGF-beta 1 requirements for cell cycle progression are genetically separable, (b) that the two major control points in the fibroblast cell cycle (G0/G1 and G1/S) are regulated by distinct extracellular signals, and (c) that the genes regulating anchorage-independent growth need not be involved in regulating contact inhibition, focus formation, or growth factor dependence.

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